This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 9804428-2 filed in Sweden on Dec. 18, 1998; the entire content of which is hereby incorporated by reference.
1. Technical Field of the Invention
The invention relates to a method and an arrangement in a radio communication system. More precisely, the invention relates to a way of transferring messages between a first unit and a second unit in the radio communication system.
2. Description of Related Art
A typical way of transferring messages from a first unit to a second unit in a communication system is to divide a message, alternatively refered to as a data packet, into one or several frames and transfer said frames from the first unit to the second unit. The content of a frame may become corrupted during transfer from the first unit to the second unit. Thus at the receiving second unit, some kind of error detecting mechanism, typically based on cyclic redundancy check is used to detect if the content of the frame is in error. A typical way of redeeming errors that occur during transmission of frames is to use some kind of automatic repeat request (ARQ) scheme. The basic idea behind ARQ is for the receiving unit to inform the sending unit of the receipt status of received frames and then for the sending unit to retransmit those frames which were not correctly received by the receiving unit. In TIA/EIA IS-136 a variant of ARQ is defined for a digital control channel (DCCH) in the downlink direction, i.e. for transfer of messages from a base station to a mobile station, and for a digital traffic channel (DTC) in both the downlink and the uplink direction. In this variant of ARQ, the sending party controls how often the receiving party reports the receipt status of received frames by setting a bit called the Polling Indicator (PI) to request a STATUS frame from the receiving unit.
U.S. Pat. No. 5,699,367 discloses a retransmission method in a communication system wherein data packets are transmitted over a connection comprising cascaded links that have different properties with respect to cost, data rate or transmission quality. One of the cascaded links is considered to be the most sensitive link. According to the method, only packets actually disturbed in the sensitive link are retransmitted over the sensitive link at the same time as required storage capacity in relay stations connecting the sensitive link to nonsensitive links is reduced. Errors occuring in the sensitive link will cause retransmission over nonsensitive links of the connection as well, but this is of less importance since the nonsensitive links have a high throughput and/or low costs.
The problem dealt with by the present invention is to provide a more flexible way of performing a message transfer transaction in which at least one message is transferred in at least one frame from a first unit to a second unit in a radio communication system.
The problem is solved essentially by a method and arrangement in which a mode of informing the first unit of frame receipt status at the second unit is selected based on prevailing conditions for radio communication between the first unit and the second unit.
More specifically, the problem is solved in the following manner. Properties of radio signals exchanged between the first unit and the second unit are measured. The mode of informing the first unit of the frame receipt status at the second unit during the message transfer transaction is selected based on the measured radio signal properties. The at least one frame is transferred from the first unit to the second unit while the first unit is informed of the frame receipt status at the second unit in accordance with the selected mode of informing.
One general object of the invention is to provide a more flexible way of performing a message transfer transaction in which at least one frame is transferred from a first unit to a second unit in a radio communication system.
A more specific object of the invention is to provide a way of performing a message transfer transaction in which a mode of informing the first unit of frame receipt status at the second unit may be selected based on the prevailing conditions for radio communication between the first unit and the second unit.
An advantage afforded by the invention is that use of bandwith as well as transaction duration can be reduced when performing a message transfer transaction in good conditions for radio communication, while still providing a required message transfer robustness when performing a message transfer transaction in bad conditions for radio communication.